What does vibration really feel like or sound like on lift?

Have an 05 TJ with a 4.5" short arm RE lift on it. CV shaft etc. I
didn't cut any corners. measured pinion angle, adjusted upper control
arms, etc. Been fine for a couple years.

I am wondering what does a vibration feel like? Is it a contant vibe
or pulsing?

I am getting a weird almost harmonic minor vibration around 70mph and
up. About every 2 seconds, for a fraction of a second the harmonic
vibration "pulses". Sorta like "Whoam, Whoam, Whoam, etc".

I am finding it hard to describe. LOL.

Any help?

If you have ever used M/T tires, you will have noticed a vibration due to
the tires at very very low speeds (1-2)mph.
Driveshaft vibrations will feel almost the same, but in higher speeds (~10
mph or above). Because the feel is similar, if you do the lift and switch
to M/T tires at the same time, you won't be able to tell for sure if you
have driveshaft vibrations, unless they are very severe, or you know exactly
what to feel for.

Incorrect pinion angles, will have as a result the driveshaft to increase -
decrease rotation speed, twice per driveshaft turn, or 2*[axle ratio] times
per wheel revolution.
For example, if you have 4.10:1 gears, the driveshaft will pulse 8.2 times
per wheel revolution.

Since the wheels rotate with almost constant speed, the fluctuations of the
driveshaft speed are transmitted to the clutch and crankshaft of the engine,
via the gearbox.
So this will give you the impression that the engine is not running
smoothly.

Besides that, it transmits a vibration to the entire car body, which is
proportional in frequency with vehicle speed, and in strength with the power
applied to the wheels.
It may feel as one or two cylinders are constantly not firing. But as speed
increases it may be heard as a low pitch whine (lower pitch than the whine
you get from the differential gears or the transmission or the tires).

You may have to experiment with the pinion angles to find the angle that
makes the engine feel smoother running on all driving conditions (cruising,
acceleration, compression braking).

Bill Spiliotopoulos,
'96 XJ,
'06 TJ.


"ULB" > wrote in message
...
> Have an 05 TJ with a 4.5" short arm RE lift on it. CV shaft etc. I
> didn't cut any corners. measured pinion angle, adjusted upper control
> arms, etc. Been fine for a couple years.
>
> I am wondering what does a vibration feel like? Is it a contant vibe
> or pulsing?
>
> I am getting a weird almost harmonic minor vibration around 70mph and
> up. About every 2 seconds, for a fraction of a second the harmonic
> vibration "pulses". Sorta like "Whoam, Whoam, Whoam, etc".
>
> I am finding it hard to describe. LOL.
>
> Any help?
>

Yes, just before it pole-vaults the car and you cart wheel down the
road.

"ULB" > wrote in message
...
> Have an 05 TJ with a 4.5" short arm RE lift on it. CV shaft etc. I
> didn't cut any corners. measured pinion angle, adjusted upper control
> arms, etc. Been fine for a couple years.
>
> I am wondering what does a vibration feel like? Is it a contant vibe
> or pulsing?
>
> I am getting a weird almost harmonic minor vibration around 70mph and
> up. About every 2 seconds, for a fraction of a second the harmonic
> vibration "pulses". Sorta like "Whoam, Whoam, Whoam, etc".
>
> I am finding it hard to describe. LOL.
>
> Any help?
>


** Posted from http://www.teranews.com **

On Mon, 05 May 2008 14:06:46 -0700, L.W.(ßill)Hughes III wrote:

> Yes, just before it pole-vaults the car and you cart wheel down the
> road.

Yes what?

If you don't have a sensible answer -- preferably from experience or
verified documentation -- don't attempt humour. You don't possess a humour
module.



>
> "ULB" > wrote in message
> ...
>> Have an 05 TJ with a 4.5" short arm RE lift on it. CV shaft etc. I
>> didn't cut any corners. measured pinion angle, adjusted upper control
>> arms, etc. Been fine for a couple years.
>>
>> I am wondering what does a vibration feel like? Is it a contant vibe
>> or pulsing?
>>
>> I am getting a weird almost harmonic minor vibration around 70mph and
>> up. About every 2 seconds, for a fraction of a second the harmonic
>> vibration "pulses". Sorta like "Whoam, Whoam, Whoam, etc".
>>
>> I am finding it hard to describe. LOL.
>>
>> Any help?
>>
>>
>>
> ** Posted from http://www.teranews.com **

--
"Enlisted men are stupid, but extremely cunning and sly, and bear
considerable watching."

-- Army Officer's Guide

sounds like wheel bearing or badly cupped tires
my bet is its tires esp. if they are bf Goodrich's triple wall tire

ULB wrote:

> Have an 05 TJ with a 4.5" short arm RE lift on it. CV shaft etc. I
> didn't cut any corners. measured pinion angle, adjusted upper control
> arms, etc. Been fine for a couple years.
>
> I am wondering what does a vibration feel like? Is it a contant vibe
> or pulsing?
>
> I am getting a weird almost harmonic minor vibration around 70mph and
> up. About every 2 seconds, for a fraction of a second the harmonic
> vibration "pulses". Sorta like "Whoam, Whoam, Whoam, etc".
>
> I am finding it hard to describe. LOL.
>
> Any help?